Telephone system



Patented Mar. 27, 1934 UNITED STATES PATENT; OFFICE Berlin, Germany,

assignors to Siemens &

Halske Aktiengesellschaft, Siemensstadt, near Berlin, Germany Application November 23, 1932, Serial No. 643,958 In Germany January 21, 1932 12 Claims.

The present invention relates to a circuit arrangement for telephone systems and more particularly to a circuit arrangement for signal transmission in such systems.

The object of the invention is to eifect signals in telephone systems in such a manner that false calls cannot occur due to line faults such as, for example, the two leads of a subscribers line coming into contact with each other.

Unnecessary seizure of connecting devices is thus avoided which otherwise may lead to interruptions in the traflic particularly in systems in which calls are stored.

This, according to the invention, is achieved by causing the calling devices in the exchange to be operated by means of an additional impulse, the transmission of which is controlled from the calling station.

The invention can be used in manually as well as automatically operated telephone systems.

Embodiments of the invention are shown in Figs. 1 and 2 of the drawing. The invention, however, is not limited to these embodiments. Only the circuit details necessary for the complete understanding of the invention have been shown.

Fig. 1 shows a telephone subscribers circuit in which the signalling is effected by line loop closing and by means of condenser current controlled from the calling station, whereas Fig. 2 shows an arrangement in which an induced impulse generated in the exchange is utilized in addition to the line loop closing.

, The arrangement according to Fig. 1 operates as follows: When the subscriber of the station SA-St lifts his receiver with the object of setting up a connection, the switchhook contacts HU are closed, thus completing the following circuit: earth, battery, winding I of relay R, contact 1t, a-lead of the connecting line, contact nsi, switchhook contacts I-IU, b-lead oi the junction line, winding II of relay R, contact 21., condenser K0, earth. The condenser K0 is charged in this circuit. Relay R, on the other hand, is not ener- 45 gized in this circuit. In order to cause relay R to operate, the subscriber has to carry out additional switching operations, namely, depressing the key TA which causes the charged condenser K0 to be connected to earth in the following circuit: earth, condenser Ko, contact 2t; Winding II of relay R, b-lead, key TA, earth. The condenser is discharged over winding II of relay R in this circuit with the result that the current passing through winding I of relay R which is connected to the a-lead is superimposed so that relay is caused to operate due to the added effect of the two windings. Relay R should not operate over the key TA and its winding I only as in such a case a signalwould be transmitted when the alead is earthed. Relay R closes its contact 51 and consequently also, in known manner, the starting circuit for a call finder AS which connects the calling line to an idle outgoing junction line. Relay R remains energized in this circuit. Furthermore, it preparatorily connects winding I of relay T to the c-lead over its contact 61'. When now an idle call finder is set to the calling line, relay T is energized in known manner and disconnects windings I and II of relay R by opening its contacts 1!. and 2t. Relay T remains energized in the test circuit over its contact 7t.

Since the further switch train for the required connection is of no importance for the present invention it will not be necessary to describe the subsequent operations in connection therewith. When the connection is released at the end of the call, the windings I and II of relay R are again connected to the leads of the connecting line and the normal condition of the system is restored.

Fig. 2 shows an embodiment of the feature of the invention in which the setting up of the calling conditions, in addition to the usual line loop closing, is accomplishedby the transmission of an induced impulse from devices provided in the exchange.

When the subscriber of the station SA-Stl wishes to set up a connection and with this object in view lifts his receiver, the switchhook contacts HUI are actuated whereupon the following circuit is closed: earth, battery, winding I of relay R1, contact ltl, a-lead, contact nsil, contacts HUI, b-lead, contact 2t1, winding I of the transformer Tr, earth. Relay R1 cannot as yet attract its armature even though its winding I is energized in this circuit.

Winding II of relay R1 is disposed in the circuit for the secondary winding II of the transformer Tr. When the subscriber of the station SASt now depresses the key TAl, the field in the circuit for winding I of the transformer Tr is dispersed and an induced impulse is transmitted from winding I of the transformer to the secondary winding II and thence to winding II of relay R1. The preenergized winding I of relay R1 over the loop formed over the subscribers line adding its efiect to the now energized winding II causes relay R1 to operate so that by closing its contacts 411 it is placed in the following locking circuit: earth, battery winding I of relay R1, contacts ltl, 4T1, earth. Relay R1 in a manner known and described in conjunction with the arrangement according to Fig. 1 causes the call finder ASl (not shown) to operate so that a not shown relay T1 is energized when the call finder has been set to the calling line. ihe actuation of contacts ltl and 2t1 disconnects windings I and II of relay R1 from the subscribers line. i

The further switch train for the completion of the connection has been omitted in the description in this case also since it has no bearing on the feature of the invention.

What is claimed is:

1. In a telephone system, a line, a relay bridged across said line, and circuit connections for enabling said relay to operate only responsive to the interconnection of the two line conductors followed by the connection of the conductors to ground.

2. In a telephone system, a line, a double. wound relay bridged across the line, means for completinga'series circuit for the relay windings to preparethe relay for operation and means for momentarily completing parallel circuits for the relay windings to operate the relay.

3. In a telephone system, a line, a double wound relay 'bridged'across the line, means for setting up a flow of current through the two relay windings in seriesto prepare the relay for operation, and means for reversing the direction of'the current flow in one of the windings to operate the relay.

"4. ma telephone system, a line, a double wound relay bridged across the line, means for setting up a momentary flow of current through the two relay windings in series to prepare the relay for operation, and means for setting up a continuous flow ofcurr'ent in the same direction as said momentary current flow in one 'of' said windings and for setting up' a momentary flow of current in the' opposite direction to the first said momentary current flow in the other of said windings topperate therelay.

5fIn a' telephone system, 'a line, a double wound relay having its windings connected to the line conductorsand to battery and ground, respectively, a condenser interspersed between the one winding and ground, means for connecting the line conductors together to charge said condenser, and means for connecting the line conductors to ground to provide adischarge path for said condenser through said one relay winding and to energize the other relay winding and thereby'operate the relay.

6. In a telephone system, a 'line, a double wound line relay, a transformer having primary and secondary windings, a battery, a circuit connecting one winding of the relay to one line conductor and one pole of the battery, a second circuit connecting the primary winding of the transformer to another line conductor and the other pole of the battery,and a'third circuit connecting the other winding of the relay across the secondary winding of the transformer.

'7. The combination with a two conductor line,

"of a battery, a condenser, a double wound relay,

circuit connections connecting one pole of said battery in series with one winding of said relay to one line conductor, and circuit connections connecting the otherpole of said battery in series with said condenser and the other winding of saidrelayto the other line conductor.

8. The combination with a line including two conductors, of a double wound relay having one winding connected to one line conductor and a source of current and the other winding connected to the other line conductor and ground, and a condenser interspersed between said other windingof the relay and ground.

9. The combination with a line including two conductors of a double wound relay having one winding connected to one line conductor and a source of current and the other winding connected to the other line conductor and ground, a condenser interpersed between said 'otlier winding of the relay andgr'ound, and switching means for connecting both line conductors directly to ground.

10. In a telephone system, a'subscribers li-ne,

a double wound line relay bridged acros's'the' line in series witha source of'curre'nt'a'nd a condenser, means controlled by acalling subscriber for completing a charging circuit" for' said condenser, and means controlled by the calling subscriber for completing a discharge circuit forsaid'condenser over which said relay "is operated.

11. In atelephone system, a subscribers line, a double wound relay having one winding connected directly to one line conductor anfldthe other winding connected inductively to another lineconductor, means responsive to the initiation of a'call on the line for differentially energizing the two windings of said relay, and means controlled by the calling subscriber for cumulatively energizing the windings of said relay cooperate the same.

12. 'A telephone system as claimed in claim 11 in which the means for cumulatively energizing the relaywindings comprises switching means at the subscribers station for connecting the'line conductors to ground.

' EDUARD WOCHINGER. 'MAXIMILIAN MATHIAS. 

